Hydrocarbon detection



Jan 27, 1959 P. J. MOORE 2,871,105

HYDROCARBONDETECTION Filed March 12, 1952 2 sheets-sheet 1 Wfl Pam/ELL rl M0095,

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United States HYDRocARoN DETEcrioN Pemell J. Moore, Houston, Tex., assignor to National Lead Company, New York, N. Y., a corporation of New Jersey Application March 12, 1952, Serial No. 27 6,203 y8 Claims. ('Cl. 23-230) This invention relates to the detection and estimation of gaseous hydrocarbons in rock material and more particularly cuttings and cores obtained in drilling wells for oil and gas.

In drilling wells in search of oil and gas, samples of the subsurface formations are commonly obtained, either as cuttlngs produced by the bit, or as cores especially taken by core bits, or both. Commonly also, such rock samples are inspected and examined for their content of gaseous, liquid and solid hydrocarbons as well as for other constituents of diagnostic importance. Examination for liquid and solid hydrocarbons usually takes the form of mspection under ultraviolet light, solvent extraction, distillation or the like, and examination for gaseous hydrocarbons usually takes the form of disintegration of the rock sample often in the presence of water, so that the pore spaces are opened up and the gaseous hydrocarbons thereby liberated, whereupon they can be withdrawn or otherwise collected for testing, generally with a so-called hot wire gas detector.

A diiiiculty with systems of determining gaseous hydrocarbons in rock samples currently in use is that the heavier gaseous hydrocarbons tend to become lost by sorption and condensation in the apparatus employed, and these heavier hydrocarbons are the very ones, as is well known, that are particularly diagnostic for oil-bearing strata.

An object of the present invention is to provide a means of testing rock samples so that heavier gaseous hydrocarbons make their full contributions to the determinations made.

Another object of the invention is to provide a process and apparatus for such. testing. capable of Speed and freedom from false and spurious results.

Other objects of the invention will appear as the description thereof proceeds.

An improved apparatus has been designed whereby the invention can be carried out, as the appended drawings serve to illustrate, in which:

Figure l is a partly cutaway drawing of a disintegration and test chamber for rock cuttings; and

Figure 2 is an lenlarged sectional View of the gas detection portion of the apparatus of Figure l; and

Figure 3 is a cross-sectional view of the structure of Figure 2 looking down from the level shown by the indicia adjacent Figure 2; and

Figure 4 is a wiring diagram for the iilaments contained in the apparatus of Figure 1. Additionally,

Figures 5 and 6 show typical results obtained with and without the apparatus ofthe present invention, depicted as well'logs ofv hydrocarbon readings against depth.

Broadly speaking, the invention contemplates the disintegration of the rock sample by mechanical action under a 'suitable liquid such as water and in a container enclosing within a single space the rock sample, the mechanicaldisintegration means, the water, an air space Iabovevthe water, and the gas vdetection means in the air space. Other investigators have used similar elements y 2,871,105 Patented Jan. 27, 1959 but always separated; for example, U. S. Patent No. 2,514,690 shows a container for effecting disintegration with spaces for water and air, but separates the gas detection means physically from the latter. The inclusion of all of these elements in a single enclosure leads to unexpected and valuable results, however, not hitherto discovered or appreciated, and makes possible the many advantages given by my invention. f

Coming now to a detailed description of the invention, reference is had to yFigure l. Herein a container 10 fitted with a lid 11 are shown. A preferable construction of these is of glass for the `container and cast brass for the lid, although other materialskmay be used. In fact, containers of the type used are available commercially in glass, heat resistingV glass, aluminum,l and stain-l less steel. Glass permits visual inspection of the process of disintegration, however, and` is therefore highly suitable. The mechanical disintegration means which I have found suitable is a steel "blade 12 driven at a high speed of about 10,000 R. P. M. lby a motor 13 through a bushing 14 in the bottom of the container y10. A grease fitting 15 permits lubrication of the bushing through a hole in the blade drive shaft; av lheavy grease free of volatile constituents should be used. A gas detector iilament'as-l sembly 16, to be described in detail later, is tted into the cap 11 and held in place by a boss 17 on the cap 11, and protected from splashing by a baffle 18.

The construction of the bale 18, which may be of stainless steel, is shown in Figures 2 and 3. Two cylinders 21 and 22, closed at one end and diifering slightly in diameter, are held tightly against the cap 11 in Figure 2 by threaded screws 23. The'cylinders are both slotted longitudinally and are disposed with the slots of one cylinder opposite the lands of ythe other, so that aA baffle arrangement is effected permitting the free convection `and diffusion of gases but stopping direct trajectories of droplets of water and solid particles of the disintegrated rock sample.

The gas detector lameuts 24 and 25, as depicted in Figures 2 and 3, are mounted inside of a slotted brass tube 26 which forms the lower end of the filament assembly 16. The slots are of such dimensions as will allow free diffusion, permeation and convection of the atmosphere of the container 10 throughout the tube 26, which it will be appreciated is within the bafe assembly 18 which in turn is within the container 10. Suitable dimensions for the slots are 0.015 wide, slotted approximately half-way through the tube 26. The arrangement of the slots as depicted in Figure 2, with two slots near the bottom and two slots near the top of the larnentsl 24 and 25, allows thermal convection to aid in the other convective and diffusive forces eifecting the gaseous interchange.

The filaments themselves are, in the form shown in Figures 2 and 3, straight platinum wires of 0.0025 to 0.004 inch in diameter. The latter size is particularly suitable, and a length of about an inch has given good results. It will be appreciated that other forms of filament can be used, for example, straight ribbons, helically coiled wire, or helically coiled ribbon. Mosthot wire gas detectors are suitable, of the type wherein the compensating filament is exposed to the same atmosphere as the detector lament, and since that particular art is relatively well-known, the variations available to those skilled in the art will not be described in detail here. One of the laments, suitably 24, is inactivated so that it will not bring about catalytic oxidation of hydrocarbons at temperatures substantially lower than the ignition temperature of the hydrocarbon at an inert surface.y A suitable means of inactivation, and one which I prefer, is to coat the lament 24!- with a very thin coating of gold by vhigher hydrocarbons.

electro-deposition. Any excess soon disappears if the filament is held at a bright red temperature for a few minutes. Other methods of inactivation are described in Philip et al. Patent No. 1,224,321, and are generally applicable here. Palladium may be substituted for the platinum in both filaments, and indeed other metals exhibiting the desired catalytic activity together with chemical inertness may be used.

The filaments are secured at their lower ends by soldering to a strrup 27 which is in turn soldered to a support rod 2S. The upper ends of the filaments are soldered to terminals 29 which, together with the support rod 2S are held in an insulated portion of the assembly 16, and connected to a three-conductor cable 19, as shown in Figure 1.

The filaments 24 and 25 are connected by means ot the cable 19 to a Wheatstone bridge arrangement shown schematically-in Figure 4. In Figire 4, the inactivated filament 24, which as is evident from the circuit diagram functions as a compensator filament, and the non-deactivated, i; e., detector filament 25 are shown, as well as two l lohm resistors 40 and 4l which together with a 2 ohm potentiometer 42 form the other half of the Wheatstone bridge. A 0-1 ma. milliammeter 43 shows the condition of balance of unbalance of the bridge, and a 0-'2 volt voltmeter 44. shows the voltage across the de tector filament 24; a good commercial D. C. voltmeter of 1000 to 2000 ohms internal resistance does not load the circuit appreciablv and is suitable. Direct current is supplied to the bridge from a battery source 45, and I prefer to use about four volts source voltage dropped through two potentiometers 46 and 47 connected as shown in the diagram of Figure 4, through a single pole double throw switch 48.

The operation of the filament and measuring circuit is as follows: ln ahydrocarbon-tree atmosphere, energizing of the circuit by applving current from source 45 will cause both filaments 24 and 25y to heat approximately equally. Any imbalance ofthe bridge can be annulled bv setting potentiometer 42 so that the milliammeter 43 reads zero. The voltage applied across the compensator filament 24, which willbe approximatelv the same as that applied across the detector filament 25 if reasonable care is exercised in constructing the filaments to equal dimensions. may be read from voltmeter 44. For the detection of methane and higher gaseous hydrocarbons, I have found a voltage of 1.1 volts at voltmeter 44 to be suitable for the case of platinum filaments of round wire 0.0040" in diameterand "/s" long. For the detection of gaseous hydrocarbons of two or more carbon atoms,

I havefound'0-65 volt to be suitable under like conditions,

methane requiring a higher temperature and therefore a higherk filament current for catalytic oxidation than the Switch 48 permits convenient use of these two filament voltages, lwhich may be adjusted to the exact values given by means of' potentiometers 46 and 47, which may be of 2 ohms resistance each for the filament dimensions inst cited and for a source voltage of 4 volts.

Now when the filaments 24 and 25 are heated as described and the' surrounding air contains combustible hydrocarbons, catalytic oxidation of the latter takes place at the surface of the detector filament 25 (but not at compensator filament 24 becauseY of its deactivation as described), whereby its temperature increases and therefore also its resistance. The bridge will no longer be balanced, and the degree of imbalance will be a measure of. the concentration of hydrocarbons in the atmosphere sur-- rounding the filament and may be read on the milliarn meter 43. The reading at a filament voltage of 1.1 volts is commonly taken as a measure of total hydrocarbons, and the difference between readings at 1.1 and 0.65 volts as a measure of methane.

In order to test a rock sample, I place about 2/5 cupful .4, of the sample, which may be cuttings, cores, or a fragment of a core, in the container 10, which has a total capacity of about 6 cupfuls, add about 2 cupfuls of water, place the lid 11 with filament assembly 16 onto the container 10, turn on the motor 13 and agitare for about two minutes. Then I turn off the motor and immediately take readings on the Wheatstone bridge at the two 'fila ment voltages described.

One of the particular advantages of this procedure in accordance with my invention is that there is a substantial equality of composition between the gas in the filament cylinder 26 and the gas in the remainder of the container above the liquid level therein, because of the fact that the cylinder 26 is actually within the container 1.0, at substantially the same temperature as the contents of container l0, and in free communication therewith as far as gases are concerned. This equality of composition permits the filament detector to give a full,l undiminished response to heavier hydrocarbons, which is something which the prior art neitherlappreciated nor taught. i do not know with complete certainty why such superior results are obtained with my arrangement and procedure, but, without limiting the invention by any discussions'of theory, I may say that I believe that prior art procedures have erred in not providing for equality of temperature between the filament housing and the disintegration chamber, in not guarding against cooling of connecting tubes, whereby condensation takes place, and in using rubber and other plastic tubes for such connections. The higher hydrocarbons which are generally associated with wet gas as distinguished from dry gas, and which as stated are of great diagnostic importance, are easily lost to detectors; they are less volatile than lower hydrocarbons and so not only have lower vapor pressures so that their maximum concentrations as gases are lower, but are readily condensed on surfaces only a few degrees lower'in temperature than their source container. Moreover, their higher molecular weight and more complexV chemical structure make for ready adsorption on rough or porous surfaces even of metal, and almost completely on surfaces of rubber and other organic plastics and elastomers commonly used as tubing. The arrangement and procedure of the present invention, it will be clear from the description herein, completely avoid these sources of loss and error. It is even possible that some ofthe higher hydrocarbons exist in the upper part of the container 10 as aerosols of liquid droplets of exceedingly fine particle size, which, supported by Brownian motion, would be carried into the filament cylinder 24' and detected, but in other' arrangements would be most readily lost by entrapment and the like. f

Whatever the explanation for thel behavior 'of my procedure and arrangement may be, ithas proved highly successful in actual field usage. Figures 5 and 6, for example, show results obtained in somel actual well. tests. Figure 5 shows two cuttings logs of a well drilled in Hidalgo County, Texas, at a depth of around 9500 feet; while Figure 6 shows two cuttings logs of a well drilled in the Union Field in.And1'ews County, Texas, at a depth of around 7800 feet.

ln these figures, both curves I represent gas detector readings made with an apparatus in which the filaments are in a housing separated from the container but con- 65 nected thereto by means of short lengths of rubb'er tubing-a standard arrangement in the cuttings logging art. The two curves II represent gas detector readings made on the same cuttings samples and made at the same time as the readings of curves I at the respective wells, but

using the procedure and apparatus of the present invention. The readings taken at 1.1 volts, corresponding to total hydrocarbons, as hereinbefore described, are shown as dotted lines, while the difference between the 1.1 volt and 0.65 volt readings, corresponding to methane alone, are shown as dashed lines.` Where the two read- 1 ings coincided, a dot-and-dash line has been used. Now in the well of Figure 5, the gas show at 9482 feet was evidently largely methane, so that both types of detectors gave about the same results. In the Well of Figure 6, the old type detector showed no particular difference in the shows at around 7800 and around 7830 feet; a minor proportion of methane is shown at both depths. In the readings taken according to the present invention, on the other hand, as shown by curve II of Figure 6, a Vast difference is apparent in the character of the two shows. It is clear that at 7830 feet something was lost to the detector in curve I, but was available to the detector in curve II. The importance of not missing indications such as shown at 7830 feet by curve II need hardly be emphasized; the apparatus and personnel needed to make on-the-spot cuttings logs such as these are costly, and the well is drilled only once, so that shows of gas must be directed with certainty or the logging is entirely wasted.

It will be clear from the above description and drawings that the invention is of great usefulness and capable of giving valuable results not heretofore obtained; and it is to be understood that various changes may be made in details of construction and operation within the spirit of the invention and the appended claims, so that I do not limit myself to the exact embodiments shown and described herein,

Having described the invention, I claim:

l. In a rock sample tester, an at least loosely closed substantially water-tight container, rock disintegration means in the lower portion of said container, hydrocarbon detection means in the upper portion of said container, and means for registering the response of said hydrocarbon detection means.

2. In a rock sample tester, an at least loosely closed substantially water-tight container, rock disintegration means in the lower portion of said container, hydrocarbon detection means in the upper portion of said container but shielded from the remainder of said upper portion by a baffle shield freely permeable to gases and impermeable to trajected particles, and means for registering the response of said hydrocarbon detection means.

3. In a rock sample tester, an at least loosely closed substantially water-tight container, rock `disintegration means in the lower portion of said container, gas detector filaments in the upper portion of said container but shielded from the remainderof said upper portion by a bathe shield freely permeable to gases and impermeable to trajected particles, and means for registering the response of said gas detector laments.

4. In a rock sample tester, an at least loosely closed substantially water-tight container, a rotary-driven bladed agitator in the lower portion of said container, gas detector filaments in the upper portion of said container but shielded from the remainder of said upper portion by a baflle shield freely permeable to gases and impermeable to trajected particles, and means for registering the response of said gas detector filaments.

5. In a rock sample tester, a jar with a lid, a rotary knife in the lower portion of the jar, driving means for said rotary knife, a closed-end cylinder provided with a multiplicity of openings and attached to the underside of said lid, a second closed-end cylinder provided with a multiplicity of openings within said rst cylinder and also attached to the underside of said lid without radial alignment of slots with those of said first cylinder, a perforated third cylinder Within said second cylinder, a catalytic hot-wire gas detector filament within said third cylinder, a compensating filament within said third cylinder and in juxtaposition to said detector filament, and an electrical resistance bridge operatively connected with said filaments to measure differences in temperature thereof.

6. A process of determining the presence of hydrocarbons in a rock sample comprising, mechanically disintegrating the rock sample under water while maintaining an enclosed air space above the water, and subjecting the air in said space after disintegration has been substantial to the action of a gaseous hydrocarbon detector while maintaining said air in said space, whereby said detector acts to test for gaseous hydrocarbons.

7. A process of determining the presence of hydrocarbons in a rock sample comprising, mixing the rock sample with a larger Volume of water, grinding the rock sample while admixed with said water to substantial disintegration while maintaining an enclosure above and in contact with the rock sample-water mixture, and `actuating a gaseous hydrocarbon detector having sensing elements within said enclosure and surrounded by the air in said enclosure promptly after substantial disintegration has taken place, whereby said detector acts to test for gaseous hydrocarbons.

8. A process of determining the presence of hydrocarbons in a rock sample comprising, mixing the rock sample with a sufficient volume of water to permit the formation of a slurry, grinding the rock sample while admixed with said water to substantial disintegration while maintaining an enclosure above and in contact with the rock samplewater mixture, permitting a gaseous hydrocarbon detector having sensing elements Within said enclosure and surrounded by the air in said enclosure to reach substantial thermal equilibrium with said air `during said grinding, and actuating said sensing elements promptly after substantial disintegration has taken place so that they respond to the presence of hydrocarbons.

Instrumentation, vol. 5, issue 6, publication date, rst quarter 1952, pages 35-36. 

2. IN A ROCK SAMPLE TESTER, AN AT LEAST LOOSELY CLOSED SUBSTANTIALLY WATER-TIGHT CONTAINER, ROCK DISTEGRATION MEANS IN THE LOWER PORTION OF SAID CONTAINER, HYDROCARBON DETECTION MEANS IN THE UPPER PORTION OF SAID CONTAINER BUT SHIELDED FROM THE REMAINDER OF SAID UPPER 